The present invention relates to a cured, siloxane-containing non-woven fiber mat having fibers of different lengths that can be suitably employed as a roofing or other building composite requiring improved tear strength.
In the building composite industry, various methods have been developed in an attempt to improve the mat strength and stability of non-woven fiberous mats. Many efforts are focused on modifying the binder systems. The following patents and publications are representative of such endeavors:
U.S. Pat. No. 4,335,186 discloses a chemically modified asphalt composition where the asphalt is reacted with a nitrogen-containing organic compound which is capable of introducing to the asphalt functional groups that can serve as reactive sites to establish a secure chemical bond between the asphalt and reinforcing fillers, blended into the asphalt, such as glass fibers and siliceous aggregates.
U.S. Pat. No. 4,430,465 relates to an article of manufacturing comprising mat fibers, such as glass fibers, that are coated with a composition comprising asphalt, an alkadiene-vinylarene copolymer, a petroleum hydrocarbon resin and a branched organic amine which is employed as an anti-stripping agent.
U.S. Pat. No. 5,518,586 provides a method of making a glass fiber mat comprising dispersing glass fibers in an aqueous medium containing hydroxyethyl cellulose to form a slurry; passing the slurry through a mat forming a screen to form a wet fiber glass mat; applying a binder comprising a urea-formaldehyde resin, a water-insoluble anionic phosphate ester and a fatty alcohol to the wet glass fiber mat; and curing the binder.
U.S. Pat. No. 5,744,229 discloses a glass fiber mat made with a polymer-reacted asphalt binder. The disclosed binder of the glass fiber mat includes an aqueous emulsion of a polymer modified asphalt produced by the reaction of asphalt, a surfactant, and a phenol-, resorcinol-, urea- or melamine-formaldehyde resin.
U.S. Pat. No. 4,500,600 describes glass fibers coated with a size composition comprising xcex3-aminopropyltriethoxysilane and an alkoxysilane.
In addition to modifying the binder systems, some efforts have focused on increasing the mat strength through the use of fibers having different lengths. For example, U.S. Pat. No. 4,472,243 provides a sheet type felt material and sheet type roofing material such as shingles and rolls made therefrom. The felt comprises 10-60 weight % glass fibers having varying lengths, 15-80 weight % cellulose fiber and 5-25 weight % binder. The binder include acrylamides, starch, urea resins, phenol resins, sodium silicates, epoxy resins, styrene-butadiene rubber, acrylic, neoprene, and acrylonitrile.
U.S. Pat. No. 5,585,432 discloses reinforced polymer composites having a uniform mixture of reinforcing fibers having a polymordal length distribution and having polymer particles distributed therein. Fillers such as silicon dioxide, calcium carbonate, magnesium oxide, CaSiO3 and mica may also be present in the polymer composite.
Although improved mat strength may be accomplished using fibers of different lengths, this improved strength typically does not hold when a shingle is formed by coating the mat with asphalt. In view of the above drawbacks with the prior art, there is still a continued need to provide a new and improved non-woven mat which has improved tear strength even after it is coated with asphalt.
The present invention provides a cured, non-woven mat that has improved tear strength which strength is also transferable to a roofing material, i.e., shingle, sheet or roll, when the inventive mat is coated with asphalt. Specifically, the inventive cured, non-woven mat comprises a mixture of fibers having different fiber lengths, which fibers contain a polysiloxane compound, and are fixedly distributed in a binder. By using the differing fiber lengths in conjunction with a polysiloxane compound, lower weight mats can be produced that render similar shingle tear properties as a higher weight mat. The extent of this improvement is dependent on the fiber lengths and the amounts of different fibers employed.
Another aspect of the present invention relates to an asphalt roofing material which includes the inventive cured, siloxane-containing non-woven mat which is coated with asphalt.
Although several methods of making non-woven fiber mats can be employed to form the inventive cure, siloxane-containing mat, a wet laid process where the fibers having differing lengths are dispersed in white water to form a wet web derived from a slurry or mat is preferred. Optionally a dispersing agent, emulsifier, lubricant, defoamer, surfactant and/or other conventional excipients can be added to the fiber containing slurry of the present invention. In a mat forming machine such as a paper pulp apparatus, e.g., a FQURDRINIER(copyright)paper machine, excess water is removed from the slurry to form the web. A binder such as disclosed in U.S. Pat. No. 6,544,611 is then applied to the wet web as a 5 to 40% aqueous solution, dispersion or emulsion by employing the use of a curtain coater or a dip and squeeze or knife edge applicator. Alternatively, the binder can be sprayed onto the binder web.
Following binder saturation of the web, excess binder is removed and a web containing a siloxane polymer is then dried and cured at a temperature of between 200xc2x0 C.-400xc2x0 C. for a period of time from a few seconds to about 5 minutes. The siloxane can be introduced after or in admixture with the binder solution, or, if desired, a portion or all of the siloxane can be introduced into the fiber size or slurry before addition of the binder. The siloxane component is employed in the form of a solution, suspension emulsion or dispersion in water or in an organic solvent such as isopropanol, cyclohexanol or other inert organic solvent. For the purposes of the present invention, a coating of polysiloxane or asphalt can be added as a top coat on the cured mat.